Design and Analysis of Engine and Chassis Mounting Bracket · Design and Analysis of Engine and...

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Design and Analysis of Engine and Chassis Mounting Bracket

Vidyasagar Kadam1, Prof.A.C.Mattikali2 1M.Tech.,Mechanical Engg. Dept., MMEC, Belagavi

2 Assistant Prof. Mechanical Engg. Dept. MMEC, Belagavi

Abstract— The objective of this project is to carry out the static analysis of front engine mounting bracket to calculate deformation and stress in the component for different load conditions along x, y,

z- direction using numerical analysis. And even to carry out modal analysis of front engine mounting

bracket using numerical model to determine natural frequency and different mode shapes. Weight and

stiffness optimization of front engine mounting bracket on basis of stress build up in bracket.

It was statically and dynamically analyzed using simulation software Altair Hypermesh and Ansys.

Static analysis is to find out the total amount of stress and displacement of engine front engine

mounting bracket. Dynamic analysis is to find out the natural frequency of front engine mounting

bracket. Optimization is based on Ansys linear static and dynamic modal analysis results, which can

be used to enhance the efficiency of design process. Considering the result obtained from

optimization, geometric modal was modified and iterated until satisfactory results were achieved. The

process is repeated until all specified criteria are met.

The process helps in finding the optimized design for the front engine mounting bracket in which it

has the best performance without any failure and with minimum loads acting on the front engine

mounting bracket. After implementing optimization, weight of the front engine mounting bracket will

be reduced. FEA also be carried out on optimized design of the front and rear engine mounting

bracket check whether the optimized design is safe or not. Final results are more optimize than

existing design.

Keywords— Front engine mounting bracket; Static and Modal analysis; G-force, FEA, Optimization,

Hypermesh, Ansys,

I. INTRODUCTION

An engine mount is a connecting link between vehicle chassis and engine. The engine excitation

forces arising from firing pulse and unbalanced forces are widely considered among the main

vibration sources for the road vehicles. Correct positioning and geometry of the mount brackets on the

chassis ensures a good performance and ride quality. The brackets on the frame that support the

engine undergoes high static and dynamic stresses and even the huge amount of vibrations, as the

vehicle intend to be high a performance vehicle. Hence, by careful designing and analysis of the

mount bracket, dissipation of vibrational energy and keeping the stresses under a predetermined level,

the safety could be achieved.

There are two essential but conflicting criteria that engine must satisfy. First, to control the idle

shake and engine mounting resonance, the engine should be stiff and highly damped. Also, the motion

resulting from load conditions such as travel on bumpy roads must be controlled by it, like a shock

absorber. And secondly, for a small amplitude excitation over the higher frequency range, a compliant but lightly damped mount is required for vibration isolation and passenger comfort.

In an automotive vehicle, the engine rests on brackets which are connected to the main-frame

or the skeleton of the car. Hence, during its operation, the undesired vibrations generated by the

engine and road roughness can get directly transmitted to the frame through the brackets. This may

cause discomfort to the passenger(s) or might even damage the chassis. When the operating frequency

or disturbance approaches the natural frequency of a body, the amplitude of Vibrations gets

magnified. This phenomenon is called as resonance. If the brackets have their resonance frequencies

International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 02, Issue 10; October - 2016 [ISSN: 2455-1457]


close to the operating engine frequencies, then the large amplitude of vibration may cause its fatigue

failure or breakage, thus reducing its estimated or desired life.

The mounting of the engine should be well constrained and the mount brackets need to be light-

weight and designed to safely bear the inertial loads and maximize vibration-transmission.FEA has

been done to check the frequency and loading response of the brackets before finalizing the design.

Mass optimization has been carried out to save material and reduce the weight. The modified designed

has been re-analyzed using FEA before finalization.

II. OBJECTIVE

Design and development of front engine mounting brackets. Carry out static analysis of front

engine mounting bracket to calculate deformation and stress in the component for different load

condition along x, y, z-direction using numerical analysis. Carry out modal analysis of front engine

mounting bracket using a numerical model to determine natural frequency and different mode shape.

Weight and stiffness optimization of front engine mounting bracket on basis of stress builds up in

brackets.

III. METHODOLOGY

At first engine mounting brackets theoretical study is done. To sustain the vibrations caused by

engine as well as bumps from tires due to uneven road surfaces and support the Engine and power

train is the overall purpose of engine mounting bracket. Identified key areas for modification are. The

3-Dimensional model is prepared for Bracket, insulator with the help of constraints of the design and

then assembly of mounting bracket and insulator at proper resting surfaces of chassis and power-train

are carried out.

In present work, Static analysis and modal analysis of the engine mounting brackets are carried

out. The work is mainly focus on the weight optimization of the bracket, safety factor and sensitivity

curve. The optimization of the brackets is based on the stress builds in brackets and value of the stress

should be less than yield stress.

IV. DESIGNING OF FRONT ENGINE MOUNTING BRACKET

The front engine mounting bracket mainly support to engine of the vehicle and it takes 30% load

of the total weight to manufacture the front engine mounting bracket casting manufacturing process is

used. Figure 4.1 shows 2D drafting of front engine mounting bracket and developed 3D design model

of the same, which shows to resting position engine and chassis resting position. The rubber pad is

designed to absorb vibration induced by engine or road which is assembled in between mounting

bracket and chassis. In the design of rubber pad taking care of there is no contact in between two

metal sheets at emergency condition i.e. sudden break and acceleration for this stoppers are designed,

studs are used for assembly purpose. The rubber insulator is sandwich in between the two metal sheets

whose main function to absorb the shocks and vibration shown in figure 4.2 with the assembly of front

engine mounting bracket is done by nut and bolts and washer for tightening purpose.



Figure 4.1. 2D drafting and 3D model of front engine mounting bracket

Figure 4.2. Rubber pad for mounting bracket and assembly of front engine mounting bracket

V. STATIC ANALYSIS FOR FRONT ENGINE MOUNTING BRACKET

5.1 Static analysis for base model of front engine mounting bracket

The front engine mounting brackets undertake 30% load of total weight of engine since it important to

design bracket from the safe working point of view.

Types of load cases:

The engine mounting bracket is usually subjected to different loading conditions i.e. acceleration,

breaking, jerk and torque so that this load cases are taken in static analysis at different co-ordinate

axes which usually indicates dynamic effect. This condition are on X=4g load, Y=3g load and Z=6g

load.

1. First Load case:- X=4g=5003.1 N

2. Second load case:- Y=3g=3752.325 N

3. Third load case:- Z=6g=7504.65 N

For first load case (X=4g):

Type of analysis:-Static structural.

Expected output:-Displacement & Stress.

Software used:-ANSYS Workbench 14.5.



Geometry is created by using CATIA V5R16.It is imported in igs format in ANSYS Workbench.

Mesh size selected is 5mm.

Material assigned:-SG IRON 450/10.

Type of manufacturing bracket: Casting.

Material properties as:-Modulus of Elasticity (E)=51.7e MPa, Poisson’s Ratio (µ)=0.275 &

Density( )=97.1e tonnes /mm3.

Load on bracket at load condition x=4g:-5003.1 N

Yield Stress:-310 Mpa.

Meshing Type:-Tetrahedral meshing.

No. of nodes:-4298.

No. of elements:-15600.

Weight of bracket: 3.024 Kg.

Boundary Conditions:-The one end of the bracket is fitted with the engine resting surface other end is

fitted on chassis resting surface and bracket is assembles by nut and bolt since the washer is created at

region A and it is fixed also load is applied along direction of x-co-ordinate on washer at region B

shown in figure 5.1.

Figure 5.1. Boundary condition for first load case (at x=4g) and meshing of front engine mounting bracket

Figure 5.2. Displacement & von-mises stress plots for front

engine mounting bracket (at x=4g)



Results:-

1. Maximum Deflection= 0.1632 mm

2. Maximum Von –Mises stress= 120.54 MPa.

For second load case (Y=3g):

Boundary Condition: The fixing location at region A of bracket is same as per previous but load is

applied along direction of y-co-ordinate on washer at region B shown in figure 5.3.

Figure 5.3. Boundary Condition for second load case (at y=3g)

Figure 5.4. Displacement & Von-mises stress plots for front engine mounting bracket (at y=3g)

Results:-

1. Maximum Deflection= 0.025277mm


For third load case (Z=6g):


applied along direction of z-co-ordinate on washer at region B shown in figure 5.5.



Figure 5.5. Boundary condition for third load case (at z=6g)

Figure 5.6. Displacement & von-mises stress plots for front engine mounting bracket (at z=6g)

Results:-


2. Maximum Von –Mises stress= 240.76MPa.

5.2 Static analysis of first optimized front engine mounting bracket

In first case, the maximum stress builds up in all three load condition is 240.76Mpa along z-co

ordinate axes, this value is comparatively less than yield stress since we remove the material where

the less stresses builds-up. For first modification we reduce the thickness of chassis resting portion of

bracket by 5mm thickness which is shown in the figure 5.7.



Figure 5.7. Structural optimization of front engine mounting bracket

Weight of bracket: Due to reduce in thickness of region B the weight of bracket gets reduced by 10.06

% of base model and which comes to 2.72 kg. In the boundary condition fixed the hole at region A

and load applied on region B in direction of X co-ordinate as shown in figure 5.1.

For first load case(X=4g):

Figure 5.8. Displacement & von-mises stress plots for first iteration of front engine mounting bracket (at x=4g)

Results:-

1. Maximum Deflection= 0.19305mm


For second load case (y=3g):


applied along direction of y-co-ordinate on washer at region B shown in figure 5.3.



Figure 5.9. Displacement & von-mises stress plots for first iteration of front engine mounting bracket (at y=3g)

Results:-



For Third load case (Z=6g):


applied along direction of z-co-ordinate on washer at region B shown in figure 5.5.

Figure 5.10. Displacement & von-mises stress plots for first iteration of front engine mounting bracket (at z=6g)

Results:-



5.3 Static analysis of second optimized front engine mounting bracket:

The maximum von-mises stress builds up in this analysis is 288.84Mpa and the yield stress is

310Mpa. The maximum stress value is less than the von-mises stress since we have option to

optimized this bracket where the less von-mises stress builds up so we remove the thickness by 6mm

of base model from region B and also remove the supporting member at region A which is shown in

figure 5.11.



Figure 5.11. Structural optimization of front engine mounting bracket

Weight of bracket: Due to reduce in thickness of region B and also remove the supporting member

from region A the weight of bracket gets reduced by 13.7 % of base model and which comes to 2.64

kg. In the boundary condition fixed the hole at region A and load applied on region B in direction of X

co-ordinate as shown in figure 5.1.

For first load case(X=4g):

Figure 5.12. Displacement & von-mises stress plots for second iteration of front engine mounting bracket (at x=4g)

Results:-



For second load case (y=3g):


applied along direction of y-co-ordinate on washer at region B.



Figure 5.13. Displacement & von-mises stress plots for second iteration of front engine mounting bracket (at y=3g)

Results:-



For Third load case (z=6g):


applied along direction of z-co-ordinate on washer at region B.

Figure 5.14. Displacement & von-mises stress plots for second iteration of front engine mounting bracket (at z=6g)

Results:-



VI. MODAL ANALYSIS FOR FRONT ENGINE MOUNTING BRACKET

The vibrations induced by the road or the engine at idle are typically at the frequencies in below 30 Hz

or in range in between the 30-250Hz .Since to the engine mount bracket should be stiff and highly

damped. Considering the other uncertain causes of vibrations during the actual vehicle and front and

rear engine mounting bracket life cycle a factor of safety is considered and the Natural frequency

above the 250Hz was decided as a target first natural frequency of both front and rear engine



mounting bracket. Factors deciding the natural frequency of Front and rear engine mounting bracket

are given below,

Vibrations induced by the road.

Vibrations coming from engine.

Figure 6.1. Natural frequencies for different made shapes of base modal of front engine mounting bracket.

Figure 6.2. 1st mode shape and 2nd mode shape

Figure 6.3. 3rd mode shape and 4th mode shape



Figure 6.4. 5th mode shape and 6th mode shape

VII. RESULTS

Table 7.1 Von-mises stress and deformation for front engine mounting bracket

Table 7.2 Natural frequencies (hz) for front engine mounting bracket for different mode shapes for different iteration.



VIII. CONCLUSION

Static analysis has been carried out for different load cases and it is observed that even under

maximum loading condition the engine mounting brackets are safe. Since, the stress levels are below

yield stress Also the maximum deformation developed by front engine mounting bracket is less than

acceptable deformation i.e. 2mm hence it is safe bracket.

Modal analysis of engine mounting brackets are performed and it is found that the minimum

fundamental natural frequency among front engine mounting bracket is 946.52 Hz which is greater

than the excitation frequency i.e.250 Hz, hence the engine mounting brackets are safe.

The design has been successfully optimized from its preliminary stage which gives high

quality engine mounting brackets at a lower cost.

IX. AKNOWLEDGEMENT

I would like to express my deep gratitude and sincere regards to all who helped me a lot to

submit this dissertation work on “ Design and analysis of engine and chassis mounting bracket”. And I

would like to express my sincere regards and gratitude to the entire staff members in Mechanical

Department of MMEC, Belagavi for their excellent, valuable suggestions and encouragement to take

up this project and complete this project work successfully.

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